KR102262227B1 - Directional backlights, backlight displays and methods - Google Patents

Abstract

Directional backlights, backlight displays, and methods of operating a directional backlight employ a diffraction grating to provide emitted light that is collectively scattered by the grating having uniform intensity and angular spread. A directional backlight includes a light guide configured to guide a plurality of guided light beams and a light source configured to provide a plurality of guided light beams having different radial directions. The directional backlight further includes a diffraction grating array configured to scatter a portion of the guided lightbeam of the plurality of guided lightbeams as emitted light having a uniform intensity and angular spread across the light guide surface. The backlit display further includes an array of light valves configured to modulate the emitted light to provide a displayed image.

Description

Directional backlights, backlight displays and methods

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application No. 62/476,781, filed March 25, 2017, which is incorporated herein by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

N/A

BACKGROUND Displays, and particularly 'electronic' displays, are an almost ubiquitous medium for communicating information to users of a variety of devices and products. For example, electronic displays include mobile phones (eg, smart phones), watches, tablet computers, mobile computers (eg, laptop computers), personal computers and computer monitors, automotive display consoles, camera displays, and substantially It can be found in a variety of devices and applications, including, but not limited to, non-mobile as well as a variety of other mobile display applications and devices. Electronic displays generally employ differential patterns of pixel intensity to represent or display the image or similar information being communicated. A differential pixel intensity pattern can be provided by reflecting light incident on the display, as in the case of passive electronic displays. Alternatively, the electronic display may provide or emit light to provide a differential pixel intensity pattern. Electronic displays that emit light are often referred to as active displays.

It is an object of the present invention to provide a directional backlight, a backlight display and a method.

A directional backlight according to an embodiment of the present invention includes a light guide configured to guide light beams;

a light source configured to provide a plurality of guided light beams having different radial directions within the light guide; and

an array of diffraction gratings spaced apart from each other on a surface of the light guide, the diffraction gratings of the diffraction grating array scattering a portion of a guided lightbeam of a plurality of the guided lightbeams as emitted light having an intensity, a principal angular direction, and an angular spread. comprising the diffraction grating array configured to

The emitted light collectively scattered by the diffraction gratings of the diffraction grating array is configured to have a uniform intensity and angular spread across the light guide surface.

The present invention has the effect of providing a directional backlight, a backlight display, and a method.

Various features of examples and embodiments in accordance with the principles described herein may be more readily understood by reference to the following detailed description taken in connection with the examples shown in the accompanying drawings in which like reference numerals indicate like structural elements.
1A shows a perspective view of a multiview display in an example, in accordance with an embodiment consistent with the principles described herein;
1B shows a graphical representation of the angular component of a light beam having a particular principal angular direction corresponding to the viewing direction of a multiview display in an example, in accordance with an embodiment consistent with the principles described herein.
2A shows a cross-sectional view of a diffraction grating in an example, in accordance with an embodiment consistent with the principles described herein.
2B shows a cross-sectional view of an example tilted diffraction grating, in accordance with an embodiment consistent with the principles described herein.
3A shows a top view of a directional backlight in an example, in accordance with an embodiment consistent with the principles described herein.
3B shows a cross-sectional view of a portion of a directional backlight in an example, in accordance with an embodiment consistent with the principles described herein.
3C shows a perspective view of a directional backlight in an example, in accordance with an embodiment consistent with the principles described herein.
4A shows a top view of a portion of a directional backlight in an example, in accordance with an embodiment consistent with the principles described herein.
4B shows a top view of a portion of a directional backlight in an example, in accordance with another embodiment consistent with the principles described herein.
5 shows a top view of a pair of diffraction gratings in an example, in accordance with an embodiment consistent with the principles described herein.
6 shows a top view of a directional backlight in an example, in accordance with an embodiment consistent with the principles described herein.
7A illustrates a top view of a directional backlight including pseudo-reflection mitigation in an example, in accordance with an embodiment consistent with the principles described herein.
7B shows a top view of a directional backlight including pseudo-reflection mitigation in an example, in accordance with another embodiment consistent with the principles described herein.
8 shows a block diagram of a backlit display in an example, in accordance with an embodiment consistent with the principles described herein.
9 shows a flow diagram of a method of directional backlight operation in an example, in accordance with embodiments consistent with the principles described herein.
Certain examples and embodiments may have other features in addition to or included in place of the features shown in the figures noted above. These and other features are described below with reference to the drawings above.

Examples and embodiments in accordance with the principles described herein provide directional backlighting as well as backlit displays that use directional backlighting to display images. In particular, embodiments consistent with the principles described herein provide a directional backlight configured to emit light with uniform intensity and angular spread over the range of the directional backlight. Further, in accordance with some embodiments, provided directional backlights may employ uncollimated or substantially uncollimated illumination. In various embodiments, the directional backlight employs diffractive scattering to provide emitted light by diffractive scattering. Characteristics of the diffraction grating are configured to determine the principal angular direction of the emitted light as well as the intensity and angular spread. The diffraction grating characteristics are varied as a function of the position of the diffraction grating to provide a uniform intensity and angular spread of emitted light collectively scattered by the diffraction grating. Uniform intensity and angular spread of the emitted light can provide, for example, a backlit display with uniform brightness over a wide range of viewpoints.

In some embodiments, a backlit display employing a directional backlight may be a two-dimensional (2D) display and the displayed image is a 2D image. In another embodiment, the backlight display may be a multi-view display and the displayed image is a multi-view image. When the backlight display is a multi-view display, the emitted light may include a plurality of directional light beams having different principal angular directions corresponding to respective different viewing directions of the multi-view image.

Herein, a 'two-dimensional display' or a '2D display' is defined as a display configured to provide substantially the same view of an image regardless of the direction in which the image is viewed (ie within a predefined viewing angle or range of a 2D display). do. Conventional liquid crystal displays (LCDs) found in smartphones and computer monitors are examples of 2D displays. In contrast herein, a 'multiview display' is defined as an electronic display or display system configured to provide different views of a multiview image in or from different viewing directions. In particular, different views may represent different perspective views of a scene or object in the multiview image. The use of the directional backlights and backlit displays described herein may include mobile phones (eg, smart phones), watches, tablet computers, mobile computers (eg, laptop computers), personal computers and computer monitors, automotive display consoles, cameras displays, and a variety of other mobile display applications and devices, as well as substantially non-mobile.

1A shows a perspective view of a multiview display 10 in an example, in accordance with an embodiment consistent with the principles described herein. As shown in FIG. 1A , the multi-view display 10 includes a screen 12 for displaying a multi-view image to be viewed. Screen 12 may be, for example, a phone (eg, mobile phone, smart phone, etc.), tablet computer, laptop computer, computer monitor of a desktop computer, camera display, or electronic display of substantially any other device. may be a display screen of

The multi-view display 10 provides different views 14 of the multi-view image in different viewing directions 16 with respect to the screen 12 . The viewing direction 16 is shown as arrows extending from the screen 12 in a variety of different major angular directions; The different views 14 are shown as shaded polygonal boxes at the end of the arrows (ie depicting the view direction 16 ); By way of example and not limitation in all, only four views 14 and four view directions 16 are shown. Although different views 14 are shown in FIG. 1A as being on the screen, when the multi-view image is displayed on the multi-view display 10 , the view 14 is not what it actually appears on or near the screen 12 . Take note. The depiction of views 14 on screen 12 is merely for simplicity of explanation and is intended to represent viewing the multiview display 10 from each of the viewing directions 16 corresponding to a particular view 14 . . A 2D display is a single view of the displayed image (eg, one view similar to view 14 ) as opposed to a different view 14 of the multiview image where the 2D display is typically provided by the multiview display 10 . may be substantially similar to the multi-view display 10, except that it is configured to provide

A light beam having a direction of view or equivalently corresponding to the view direction of a multiview display generally has a principal angular direction given by the angular component {θ, φ} by definition herein. The angular component θ is referred to herein as the 'elevation component' or 'elevation angle' of the light beam. The angular component φ is referred to as the 'Azimus component' or 'Azimuth angle' of the light beam. By definition, the elevation angle θ is the angle in a vertical plane (eg perpendicular to the screen plane of a multiview display), and the azimuth angle φ is the angle in the horizontal plane (eg, a multiview display). parallel to the plane of the screen).

1B illustrates a light beam 20 having a particular principal angular direction corresponding to the view direction of the multiview display (eg, view direction 18 in FIG. 1A ) in the example, in accordance with embodiments consistent with the principles described herein. ) is a graphical representation of the angular component {θ, φ}. Also, the light beam 20 is emitted or emanated from a particular point by definition herein. That is, by definition, light beam 20 has a central ray associated with a particular origin within the multiview display. Figure 1b also shows the origin O of the light beam (or direction of view).

Also, herein, the term 'multiview' used in the terms 'multiview image' and 'multiview display' refers to a plurality of views representing different perspectives or including angular disparity between the views of the plurality of views. Defined. Also, by definition herein, the term 'multiview' herein explicitly includes two or more different views (ie at least three views and generally three or more views). Thus, a 'multiview display' as employed herein is clearly distinct from a stereoscopic display which includes only two different views to represent a scene or image. However, while multiview images and multiview displays contain two or more views, by definition herein, a multiview image is stereoscopic by selecting only two of the multiview views for simultaneous viewing (ie, one view per eye). Note that it can be viewed as an image pair (ie on a multiview display).

A 'multiview pixel' is defined herein as a set of pixels representing a 'view' within each view of a plurality of different views of a multiview display. In particular, a multi-view pixel may have an individual pixel that corresponds to or represents a view pixel in each of the different views of the multi-view image. Also, a pixel of a multiview pixel is, by definition herein, a so-called 'directional pixel' in that each pixel is associated with a given direction of view of the corresponding one of the different views. Further, according to various examples and embodiments, different view pixels represented by pixels of a multi-view pixel may have equivalent or at least substantially similar positions or coordinates in each of the different views. For example, a first multiview pixel may have a respective view pixel corresponding to a view pixel located _{at {x 1} , y ₁ } in each of the different views of the multiview image, while the second multiview pixel may have a different view In each one can have a respective view pixel corresponding to the view pixel located _{at {x 2} , y _{2 }, and so on.}

In some embodiments, the number of view pixels of a multiview pixel may be equal to the number of views of a multiview display. For example, a multiview pixel may provide 8 view pixels in association with a multiview display having 8 different views. Alternatively, a multiview pixel may provide 64 view pixels associated with a multiview display having 64 different views. In another example, a multiview display may provide an 8×4 view array (ie, 32 views), and the multiview pixels may include 32 view pixels (ie, one for each view). Further, in accordance with some embodiments, the number of multi-view pixels of the multi-view display may be substantially equal to the number of pixels that constitute a selected view of the multi-view display.

As used herein, a 'light guide' is defined as a structure that uses total reflection to guide light within the structure. In particular, the light guide may comprise a core substantially transparent to the operating wavelength of the light guide. In various instances, the term 'light guide' generally refers to a dielectric optical waveguide that employs total reflection to guide light at the interface between the dielectric material of the light guide and the material or medium surrounding the light guide. By definition, the condition for total reflection is that the refractive index of the light guide is greater than the refractive index of the surrounding medium adjacent to the surface of the light guide material. In some embodiments, the light guide may include a coating in addition to or instead of the refractive index difference described above to further facilitate total reflection. The coating may be, for example, a reflective coating. The light guide may be any of several light guides including, but not limited to, one or both of a plate or slab guide and a strip guide.

Also herein, the term 'plate' when applied to a light guide as in 'plate light guide' is defined as a sculpted or differential planar layer or sheet, often referred to as a 'slab' guide. In particular, a plate light guide is defined as a light guide configured to guide light in two substantially orthogonal directions bounded by a top and bottom surface (ie opposing surfaces) of the light guide. Also, by definition herein, the upper and lower surfaces are both separate from each other and may be substantially parallel to each other, at least in a differential sense. That is, within any differentially small section of the plate light guide, the top and bottom surfaces are substantially parallel or coplanar.

In some embodiments, the plate light guide may be substantially flat (ie, confined to a plane), and thus the plate light guide is a planar light guide. In other embodiments, the plate light guide may be curved in one dimension or orthogonal two dimensions. For example, a plate light guide may be curved in a single dimension to form a cylindrically shaped plate light guide. However, any curvature has a radius of curvature large enough to ensure that the total reflection remains within the plate light guide to guide the light.

As used herein, a 'diffraction grating' is generally defined as a plurality of features (ie, diffractive features) arranged to provide diffraction of light incident on the diffraction grating. In some examples, the plurality of features may be arranged in a periodic or quasi-periodic manner with one or more lattice spacing between the feature pairs. For example, a diffraction grating may include a plurality of features (eg, a plurality of grooves or ridges in a material surface) arranged in a one-dimensional (ID) array. In another example, the diffraction grating may be a two-dimensional (2D) array of features. The diffraction grating may be, for example, a 2D array of bumps on the material surface or holes in the surface. According to various embodiments and examples, the diffraction grating may be a sub-wavelength grating having a grating spacing or distance between adjacent diffractive features that is less than the wavelength of light to be diffracted by the diffraction grating.

As such, by definition herein, a 'diffraction grating' is a structure that provides diffraction of light incident on the diffraction grating. If light is incident on the diffraction grating from the light guide, the diffraction or diffraction scattering provided may result in 'diffraction coupling' in that the diffraction grating may couple-out the light from the light guide by diffraction, and thus as such may be referred to. The diffraction grating also redirects or changes the angle of light by diffraction (ie, diffraction angle). In particular, as a result of diffraction, light leaving the diffraction grating generally has a propagation direction different from that of light incident on the diffraction grating (ie, incident light). A change in the propagation direction of light due to diffraction is referred to herein as 'diffraction redirection'. Thus, a diffraction grating can be understood to be a structure comprising diffractive features that diffractively redirect light incident on the diffraction grating, and if the light is incident from the light guide, the diffraction grating also diffractively redirects light from the light guide. can be coupled-out.

Also, by the definition herein, a feature of a diffraction grating is referred to as a 'diffractive feature', and may be one or more of, in, or on the surface surface (ie, the boundary between two materials). The surface may be, for example, the surface of the light guide. The diffractive features may include any of a variety of structures that diffract light, including, but not limited to, one or more of grooves, ridges, holes, and bumps in, in and on the surface. For example, the diffraction grating may include a plurality of substantially parallel grooves in the material surface. In another example, the diffraction grating may include a plurality of parallel ridges rising from the material surface. The diffractive features (eg, grooves, ridges, holes, bumps, etc.) include one or more of a sinusoidal profile, a rectangular profile (eg binary diffraction grating), a triangular profile, and a sawtooth profile (eg blaze grating). may have any of a variety of cross-sectional shapes or profiles that provide diffraction, including, but not limited to, diffraction.

As described further below, a diffraction grating herein may have grating characteristics including one or more of feature spacing or pitch, orientation, and size (eg, the width or length of the diffraction grating). Further, the grating characteristics may be chosen or chosen to be a function of the angle of incidence of the light beam on the diffraction grating, the distance of the grating from the light source, or both. In particular, in accordance with some embodiments, the grating characteristics of the diffraction grating may be selected to depend on the relative position of the light source and the position of the diffraction grating.

According to various examples described herein, a diffraction grating (eg, a diffraction grating of a multiview pixel, as described below) diffractively scatters light from a light guide (eg, a plate light guide) as a light beam. or to couple-out. _{In particular, the diffraction angle θ m} provided by or of a locally periodic diffraction grating can be given by equation (1).

(1)

(One)

λ is the wavelength of the light, m is the diffraction order, n is the refractive index of the light guide, d is the distance or spacing between the features of the diffraction grating, and θ _i is the angle of incidence of the light on the diffraction grating. For simplicity, equation (1) assumes that the diffraction grating is adjacent to the surface of the light guide and that the refractive index of the material outside the light guide is 1 (ie, n _out =1). In general, the diffraction order m is given as an integer. _{The diffraction angle θ m} of the light beam generated by the diffraction grating can be given by equation (1) where the diffraction order is positive (eg, m>0). For example, a first order diffraction is provided when the diffraction order m is 1 (ie, m=1).

2A shows a cross-sectional view of a diffraction grating 30 in an example, according to an embodiment consistent with the principles described herein. For example, the diffraction grating 30 may be positioned on the surface of the light guide 40 . 2a also shows a light beam 50 incident on the diffraction grating 30 at an angle of incidence θ _{i .} The incident light beam 50 may be a light beam guided within the light guide 40 (ie, a guided light beam). Also shown in FIG. 2A is a directional light beam 60 that is diffractively generated and coupled-out by the diffraction grating 30 as a result of diffraction of the incident light beam 50 . The directional lightbeam 60 has a diffraction angle θ _m (or 'principal angular direction' herein) as given by equation (1). The diffraction angle θ _m may correspond to, for example, a diffraction order 'm' of the diffraction grating 30 , eg, a diffraction order m=1 (ie, the first diffraction order).

By definition herein, a 'slanted' diffraction grating is a diffraction grating having diffraction features that have an inclination angle with respect to the surface normal of the surface of the diffraction grating. According to various embodiments, a tilted diffraction grating may provide unidirectional scattering by diffraction of incident light.

2B shows a cross-sectional view of an example inclined diffraction grating 80 , in accordance with an embodiment consistent with the principles described herein. As shown, the tilted diffraction grating 80 is a binary diffraction grating positioned on the surface of the light guide 40, similar to the diffraction grating 30 shown in FIG. 2A . However, the inclined diffraction grating 80 shown in Figure 2b is a diffractive feature having an inclination angle γ with respect to the surface normal (shown by the dashed line) with the grating height, depth or thickness t as shown. 82). Also shown is an incident light beam 50 and a directional light beam 60 showing unidirectional diffractive scattering of the incident light beam 50 by a tilted diffraction grating 80 . Note that diffraction scattering of light in the secondary direction by the inclined diffraction grating 80 is suppressed by unidirectional diffraction scattering according to various examples. In FIG. 2B , the 'scissors' dashed arrow 90 indicates the suppressed diffraction scattering in the secondary direction by the inclined diffraction grating 80 .

According to various embodiments, the tilt angle γ of the diffractive features 82 can be selected to control the unidirectional diffractive characteristics of the tilted diffraction grating 80 , including the degree to which diffractive scattering in the secondary direction is suppressed. have. For example, the angle of inclination γ may be selected between about 20° and about 60° or between about 30° and about 50° or between about 40° and about 55°. For example, when compared to the unidirectional direction provided by the tilted diffraction grating 80 , the tilt angle γ in the range of about 30°-50° is greater than about 40 times (40x) the diffraction scattering in the secondary direction. It can provide better suppression. The thickness t of the diffractive features 82 may be between about 100 nanometers (100 nm) and about 400 nanometers (400 nm), according to some embodiments. For example, the thickness t may be between about 150 nanometers (150 nm) and about 300 nanometers (300 nm) for a lattice periodicity p in the range of about 300 nm to about 500 nanometers (500 nm).

By definition herein, a 'multibeam element' is a structure or element of a backlight or display that produces light comprising a plurality of light beams. A 'diffuse' multibeam element is, by definition, a multibeam element that generates a plurality of light beams by or using diffractive coupling. In particular, in some embodiments, the diffractive multibeam element may be optically coupled to the light guide of the backlight to provide a plurality of light beams by diffractively coupling out a portion of the light guided to the light guide. Further, by definition herein, a diffractive multibeam element comprises a plurality of diffraction gratings within a boundary or range of the multibeam element. The light beams of a plurality of light beams (or 'plural light beams') generated by the multibeam element, by definition herein, have different principal angular directions. In particular, by definition, one light beam of the plurality of light beams has a predetermined principal angular direction different from another light beam of the plurality of light beams. According to various embodiments, the spacing or grating pitch of the diffractive features in the diffraction grating of the diffractive multibeam element may be sub-wavelength (ie, less than the wavelength of the guided light).

According to various embodiments, the plurality of light beams may represent a light field. For example, the plurality of light beams may be confined to a substantially conical region of space or may have an angular spread comprising different principal angular directions of the light beams of the plurality of light beams. Thus, a given angular spread of light beams (ie multiple light beams) in combination can represent a light field.

As used herein, 'collimated light' or 'collimated lightbeam' is generally defined as a light beam in which the rays of the light beam are substantially parallel to each other in the light beam (eg, guided light in a light guide). Also, light rays that are emitted or scattered from the collimated lightbeam are not, by definition herein, considered to be part of the collimated lightbeam. Also, a 'collimator' is defined herein as substantially any optical device or apparatus configured to collimate light.

As used herein, the 'collimation factor' is defined as the degree to which light is collimated. In particular, the collimation factor, by definition herein, defines the angular spread of a ray within a collimated lightbeam. For example, the collimation factor (σ) may specify that most rays of a collimated lightbeam are within a certain angular spread (e.g., +/- σ relative to the center or principal angular direction of the collimated lightbeam). can The ray of the collimated lightbeam may have a Gaussian distribution in terms of angle, and the angular spread may be an angle determined to be 1/2 the peak intensity of the collimated lightbeam, according to some examples.

As used herein, a 'light source' is defined as a light source (eg, an optical emitter configured to generate and emit light). For example, the light source may include an optical emitter, such as a light emitting diode (LED), that emits light when activated or turned on. In particular, the light source herein may be substantially any light source, or may be a light emitting diode (LED), a laser, an organic light emitting diode (OLED), a polymer light emitting diode, a plasma-based optical emitter, a fluorescent lamp, an incandescent lamp, virtually any It may include virtually any optical emitter including, but not limited to, one or more of other light sources. The light generated by the light source may have a color (ie, may include light of a specific wavelength) or may be a range of wavelengths (eg, white light). In some embodiments, the light source may include a plurality of optical emitters. For example, the light source may be a set of optical emitters in which at least one optical emitter produces light having a color or equivalent wavelength different from or wavelength of light generated by the at least one other set or group of optical emitters. or groups. The different colors may include, for example, primary colors (eg, red, green, blue).

As used herein, the term 'unidirectional' as in 'unidirectional diffraction scattering' and 'unidirectional direction' refers to 'on one side' or 'preferentially' corresponding to a first side as opposed to another direction corresponding to a second side. It is defined as meaning 'to one-way'. In particular, 'unidirectional diffractive scattering' is defined as diffractive scattering that provides or emits light from a first side rather than a second side opposite the first side. For example, unidirectional diffractive scattering by a diffraction grating may emit light into a first (eg, positive) half-space rather than into a corresponding second (eg, negative) half-space. have. The first semi-volume may be above the diffraction grating or light guide in which the diffraction grating is located and the second semi-volume may be below the diffraction grating. Thus, one-way diffractive scattering may, for example, emit light into or towards a direction above the diffraction grating, and emit little or no light into or towards another area below the diffraction grating, for example. can A tilted diffraction grating may provide unidirectional diffractive scattering, in accordance with various embodiments described herein.

σ). 회절 격자는 각도-보존 산란 피처의 예이다. 대조적으로, 일반적인 디퓨저(예를 들어, 램버시안 산란을 갖는 또는 이에 근사한) 뿐만 아니라 램버시안 스캐터러 또는 램버시안 반사기는 본원에서 정의에 의해 각도-보존 스캐터러가 아니다.As used herein, an 'angle-preserving scattering feature' or equivalently an 'angle-preserving scatterer' refers to any element configured to scatter light in a manner that substantially preserves the angular spread of light incident on the feature or scatterer in the scattered light. It is a feature or scatterer. In particular, by definition, the angular spread (σ _S ) of light scattered by an angle-preserving scattering feature is a function of the angular spread (σ) of incident light (ie, σ _S = f(σ)). In some embodiments, the angular spread of the scattered light (σ _S ) is a linear function of the angular spread or collimation factor (σ) of the incident light (eg, σ _S = ασ and α is an integer). That is, the angular spread (σ _S ) of light scattered by an angle-preserving scattering feature may be substantially proportional to the angular spread or collimation factor (σ) of incident light. For example, the angular spread of scattered light (σ _S ) can be substantially equal to the incident light angular spread (σ) (eg, σ _{S )}

σ). A diffraction grating is an example of an angle-preserving scattering feature. In contrast, a typical diffuser (eg, having or approximate to Lambertian scattering) as well as a Lambertian scatterer or Lambertian reflector is not an angle-preserving scatterer by definition herein.

Also, as used herein, the article 'a' is intended to have its ordinary meaning in the patent field, ie, 'one or more'. For example, 'diffraction grating' means one or more diffraction gratings, and thus 'diffraction grating' means 'diffraction grating(s)' herein. In addition, as used herein, 'top', 'bottom', 'top', 'bottom', 'top', 'bottom', 'front', 'back', 'first', 'second', 'left' or Reference to 'right' is not intended to be limiting herein. As used herein, the term 'about' when applied to a value generally means within the tolerance of the equipment used to produce the value, plus or minus 10%, or plus or It can mean minus 5%, or plus or minus 1%. Also, as used herein, the term 'substantially' means most, or almost all, or all or an amount in the range of from about 51% to about 100%. Also, the examples herein are intended to be illustrative only, and are presented for purposes of discussion and not limitation.

In accordance with some embodiments of the principles described herein, a directional backlight is provided. A directional backlight is configured to emit light and may be used, for example, to illuminate a backlit display. 3A shows a top view of a directional backlight 100 in an example, in accordance with an embodiment consistent with the principles described herein. 3B shows a cross-sectional view of a portion of a directional backlight 100 in an example, in accordance with an embodiment consistent with the principles described herein. In particular, FIG. 3B may show a cross-sectional view through a portion of the directional backlight 100 of FIG. 3A with the cross-section in the x-z plane. 3C shows a perspective view of a directional backlight 100 in an example, in accordance with an embodiment consistent with the principles described herein. According to various embodiments, the illustrated directional backlight 100 may be employed as a backlight for an electronic display (or simply 'display') configured to display an image. In some of these embodiments, the electronic display may be a multi-view display and the displayed image may be a multi-view image.

The directional backlight 100 shown in FIGS. 3A-3C is configured to provide an emitted light 102 . Further, the emitted light 102 provided by the directional backlight 100 is configured to have a uniform or at least substantially uniform intensity and angle spread, in accordance with various embodiments. In particular, the intensity and angular spread of the emitted light 102 may be substantially constant regardless of its location across the directional backlight 100 . The uniform intensity and angular spread of the emitted light 102 may provide uniform brightness over the angular viewing range of, for example, a display employing the directional backlight 100 . Also, in at least some embodiments, the angular view range may be less than about 60° in one or two orthogonal directions parallel to the emitting surface or plane of the directional backlight 100, and may be much smaller in some embodiments. have.

As shown, the directional backlight 100 includes a light guide 110 . The light guide may be, for example, a plate light guide (as shown). The light guide 110 is configured to guide light along the length of the light guide 110 as guided light or more specifically as a plurality of guided light beams 112 . For example, the light guide 110 may include a dielectric material configured as an optical waveguide. The dielectric material may have a first index of refraction greater than a second index of refraction of the medium surrounding the dielectric optical waveguide. The difference in refractive index is configured to facilitate total reflection of the guided light beam 112 of the plurality of guided light beams, for example according to one or more guidance modes of the light guide 110 .

In some embodiments, light guide 110 may be a slab or plate optical waveguide comprising an elongated substantially planar sheet of optically transparent dielectric material. The substantially planar sheet of dielectric material is configured to guide the guided light beam 112 using total reflection. According to various examples, the optically transparent material of the light guide 110 may include various types of glass (eg, silica glass, alkali-aluminosilicate glass, borosilicate glass, etc.) and a substantially optically transparent plastic or polymer. may comprise or consist of any of a variety of dielectric materials including, but not limited to, one or more of (eg, poly(methyl methacrylate) or 'acrylic glass', polycarbonate, etc.) . In some examples, light guide 110 may further include a cladding layer (not shown) on at least a portion of a surface of light guide 110 (eg, one or both of an upper surface and a lower surface). have. A cladding layer may be used to further facilitate total reflection, according to some examples.

According to various embodiments, the light guide 110 includes a first surface 110 ′ (eg, a 'front' surface) and a second surface 110 ″ (eg, a 'rear' surface) of the light guide 110 . is configured to guide the guided light beam 112 according to total reflection at a non-zero propagation angle between the 'surfaces. In particular, the guided light beam 112 is configured to guide the first surface 110' of the light guide 110 at a non-zero propagation angle between the 'surfaces'. ) and the second surface 110", may propagate by reflection or 'bouncing'. Note that the non-zero propagation angle is not clearly shown in FIG. 3B for the sake of simplicity of explanation. However, FIG. 3b shows an arrow pointing into the plane of the drawing showing the general direction of propagation 103 of the guided light beam 112 along the light guide length.

As defined herein, a 'non-zero propagation angle' is an angle with respect to the surface of the light guide 110 (eg, first surface 110 ′ or second surface 110 ″). The raw propagation angle, according to various embodiments, is greater than zero and less than the critical angle of total reflection within the light guide 110. For example, the non-zero propagation angle of the guided light beam 112 is between about 10 degrees and about 50 degrees or In some examples, it can be between about 20 degrees and about 40 degrees, or between about 25 degrees and about 35 degrees. For example, the non-zero propagation angle can be about 30 degrees. In other examples, the non-zero propagation angle can be about 20 degrees. degrees or about 25 degrees or about 35 degrees Also, as long as the specific non-zero propagation angle is chosen to be less than the critical angle of total reflection within the light guide 110, the specific non-zero propagation angle may be used for a particular implementation (eg, , arbitrarily) can be selected.

3A and 3C , the directional backlight 100 further includes a light source 120 . The light source 120 is located at the input position 116 of the light guide 110 . For example, the light source 120 may be positioned adjacent to the edge or side 114 of the light guide 110 , as shown. The light source 120 is configured to provide light within the light guide 110 as a plurality of guided light beams 112 . The light source 120 also provides light such that individual guided light beams 112 of the guided plurality of light beams have different radial directions 118 from each other.

In particular, the light emitted by the light source 120 is incident on the light guide 110 and then a plurality of guided light beams 112 in a radial pattern away from the input location 116 over or along the length of the light guide 110 . ) is configured to propagate as Further, the individual guided lightbeams 112 of the guided plurality of lightbeams have different radial directions 118 from each other by the radial pattern of propagation away from the input location 116 . That is, the guided light beam 112 propagates away from a common origin (ie, the light source 120 at the input location 116 ) in different radial directions 118 , as shown. For example, light source 120 may be butt-coupled to side 114 . Butt-coupled light sources 120 may facilitate introduction of light in a fan-shaped pattern, for example, to provide different radial directions of individual guided light beams 112 . In accordance with some embodiments, the light source 120 is a 'point' at the input location 116 such that the guided light beam 112 propagates along different radial directions 118 (ie, as a plurality of guided light beams 112 ). It may be a light source or at least approximate it.

In some embodiments, the input location 116 of the light source 120 is on the side 114 of the light guide 110 at the center or near the middle (eg, nearly or approximately) of the side 114 . 3A and 3C , the light source 120 is positioned at an input location 116 that is approximately centered (eg, in the middle) on the side 114 (ie, the 'input side') of the light guide 110 . is in Alternatively (not shown), the input location 116 may be remote from the middle of the side 114 of the light guide 110 . For example, the input location 116 may be at a corner of the light guide 110 . For example, the light guide 110 may have a rectangular shape (eg, as shown), and the input location 116 of the light source 120 is a corner (eg, a rectangular shape) of the light guide 110 . for example, at the corner of the input side 114).

In some embodiments, the light source 120 may be positioned within the cavity on the side of the light guide 110 . According to various embodiments, the cavity may have a shape configured to diffuse or otherwise provide a plurality of guided light beams 112 in different radial directions 118 . 4A shows a top view of a portion of a directional backlight 100 in an example, in accordance with an embodiment consistent with the principles described herein. 4B shows a top view of a portion of a directional backlight 100 in an example, in accordance with another embodiment consistent with the principles described herein. In particular, FIGS. 4A-4B show a portion of the directional backlight 100 on the side 114 of the light guide 110 that includes the light source 120 . The light source 120 is also positioned within the cavity 122 on the light guide side 114 , as shown. 4A shows a cavity 122 having a semi-circular shape configured to diffuse a plurality of guided light beams 112 in different radial directions 118 . 4B shows a cavity 122 having a faceted or segmented linear cavity shape. Also in FIGS. 4A and 4B , the light source 120 includes a plurality of optical emitters 124 distributed along the surface of the cavity 122 . 4A-4B also show the light beam 112 guided as arrows radiating away from the cavity 122 and the light source 120 in different radial directions 118 .

In various embodiments, light source 120 is substantially any light source (eg, optical emitter) including, but not limited to, one or more light emitting diodes (LEDs) or lasers (eg, laser diodes). (124)). In some embodiments, the light source 120 may include an optical emitter 124 configured to produce substantially monochromatic light having a narrowband spectrum represented by a particular color. In particular, the color of monochromatic light may be a primary color of a particular color space or color model (eg, an RGB color model). In another example, light source 120 may be a substantially broadband light source configured to provide substantially broadband or polychromatic light. For example, the light source 120 may provide white light. In some embodiments, the light source 120 may include a plurality of different optical emitters 124 configured to provide different colors of light. The different optical emitters 124 may be configured to provide light having different, color-specific, non-zero propagation angles of the guided light corresponding to each of the different colors of light.

In some embodiments, a guided lightbeam 112 of a plurality of guided lightbeams generated by coupling light from a light source 120 to a light guide 110 may be decollimated or at least substantially decollimated. In another embodiment, the guided light beam 112 may be collimated, for example in a vertical direction (ie, the guided light beam 112 may be a collimated light beam). As such, in some embodiments, the directional backlight 100 may include a collimator (not shown) between the light source 120 and the light guide 110 . Alternatively, the light source 120 may further comprise a collimator configured to provide collimation in a plane perpendicular to the direction of propagation of the guided light beam 112 (eg, a 'perpendicular' plane). Specifically, the collimated guided light beam 112 has a relatively narrow angular spread in a plane perpendicular to the surface of the light guide 110 (eg, the first or second surface 110 ′, 110 ″). According to various embodiments, the collimator may be a lens, reflector or mirror (eg, a tilted collimator reflector), or a diffraction grating configured to collimate light from, for example, light source 120 . may include any of a variety of collimators including, but not limited to.

Also, in some embodiments, the collimator may provide collimated light of one or both of having a non-zero propagation angle and collimating according to a predetermined collimation factor. Further, when different color optical emitters are employed, the collimator provides collimated light having one or both of different, color-specific, non-zero propagation angles and different, color-specific collimating factors. can be configured to The collimator is further configured to deliver the collimated light to the light guide 110 to propagate as a guided light beam 112 in some embodiments.

Referring again to FIGS. 3A-3C , the directional backlight 100 further includes a diffraction grating array 130 spaced apart from each other on the surface of the light guide 110 . 3B and 3C , the diffraction grating array is shown on the first surface 110 ′ by way of example and not limitation. According to various embodiments, the diffraction grating array 130 is configured to emit or scatter light as the emitted light 102 . In particular, the diffraction grating 130 of the diffraction grating array is configured to scatter a portion of the guided lightbeam 112 of the plurality of guided lightbeams as the emitted light 102 having an intensity, a principal angular direction, and an angular spread. 3B and 3C, the main angular direction is shown using arrows, and the angular spread is shown by a pair of dashed lines on either side of the arrow in FIG. 3B. In Figure 3c, the angle spread is shown using a cone to show the cone angle of the angle spread. Also, in FIG. 3C , only the selective diffraction grating 130 , the corresponding guided light beam 112 , and the scattered emitted light 102 are shown for ease of illustration and not limitation.

According to various embodiments, the individual diffraction gratings 130 of the diffraction grating array generally do not intersect, overlap, or contact each other. That is, each diffraction grating 130 of the diffraction grating array is spaced apart from each other, and thus, according to various embodiments, each diffraction grating 130 is generally distinct and separate from the others of the diffraction grating 130 . .

In various embodiments, each diffraction grating 130 of the diffraction grating array has an associated grating characteristic. The grating characteristics of the diffraction grating 130 are configured to determine the intensity, principal angular direction, and angular spread of the emitted light 102 scattered by the diffraction grating 130 . Also, the grating characteristics of the diffraction grating 130 are generally of both the position of the diffraction grating 130 on the surface of the light guide 110 and the position of the light source 120 on the side 114 of the light guide 110 . It is a function. In particular, the grating characteristic of each diffraction grating 130 depends on, is defined by, or is a function of the radial direction 118 of the guided light beam 112 incident on the diffraction grating 130 from the light source 120 . . Further, the grating characteristic, in various embodiments, is determined or defined by the distance between the diffraction grating 130 and the input location 116 of the light source 120 . For example, the grating feature is the distance D between the diffraction grating 130a and the input position 116 and the radial direction of the guided light beam 112 incident on the grating 130a, as shown in FIG. 3A . It may be a function of (118a). In other words, the grating features of the diffraction grating 130 in the plurality of diffraction gratings 130 are diffraction on the surface of the light guide 110 at the input location 116 of the light source and relative to the input location 116 of the light source 120 . It depends on the specific location of the grating 130 .

3a shows two different diffraction gratings 130a, 130b with different spatial coordinates (x ₁ , y ₁ ) and (x ₂ , y ₂ ), which is a light source 120 incident on the diffraction grating 130 . It further has different grating characteristics to compensate for or account for the different radial directions 118a , 118b of the plurality of guided light beams 112 from . Similarly, the different grating characteristics of the two different diffraction gratings 130a, 130b are respectively diffracted from the light source input position 116 determined by the _{different spatial coordinates (x 1} , y ₁ ) and (x ₂ , y _{2 ).} The different distances of the gratings 130a and 130b are accounted for.

In some embodiments, the grating characteristic includes a grating depth. The grating depth may be configured to determine the intensity of the emitted light 102 scattered by the diffraction grating 130 . In some embodiments, the grating characteristics include one or both of a grating pitch and a grating orientation of the diffraction grating configured to determine a principal angular direction of the emitted light 102 scattered by the diffraction grating 130 . Here, the grating pitch is equal to the spacing of the diffractive features of the diffraction grating 130 , and the grating orientation is the coordination angle of the diffractive features with respect to the radial direction 118 of the guided light beam 112 incident on the diffraction grating 130 . . In some embodiments, the grating characteristics include one or both of a grating chirp and a curvature of the diffraction grating 130 configured to determine an angular spread of the emitted light 102 scattered by the diffraction grating 130 . In some embodiments, grating characteristics may include a combination of one or more of grating depth, grating pitch, grating orientation, grating chirp, and curvature of the diffraction grating 130 .

5 shows a top view of a pair of diffraction gratings 130 in an example, in accordance with an embodiment consistent with the principles described herein. For example, the pair of diffraction gratings 130 of FIG. 5 may be equivalent to the diffraction gratings 130a and 130b shown in FIG. 3A . In particular, as shown, a pair of diffraction gratings 130 may be positioned on the surface of the light guide 110 and may have different grating characteristics. With respect to the different grating characteristics, each diffraction grating 130 of the diffraction grating pair has the curvature and grating chirp of each diffractive feature 132 as shown. Further, the diffraction grating 130 has different grating orientations corresponding to different radial directions 118 of the incident guided light beam 112 as shown. As noted above, the different grating characteristics are the location of each diffraction grating 130 of the pair of diffraction gratings on the surface of the light guide 110 and the light source 120 providing the guided light beam 112, in accordance with various embodiments. It is a function of both positions (not shown in Figure 5).

The spacing or grating pitch of the diffractive features 132 in the diffraction grating 130 may be sub-wavelengths (ie, less than the wavelength of the guided light beam 112 ) in accordance with some embodiments. In some embodiments, the diffraction grating 130 may include a plurality of different gratings or sub-gratings. According to some embodiments, the diffractive features 132 of the diffraction grating 130 may include one or both of grooves and ridges spaced apart from each other. The grooves or ridges may comprise the material of the light guide 110 , for example the grooves or ridges may be formed in the surface of the light guide 110 . In another example, the grooves or ridges may be formed from a material other than the light shield material, eg, a film or layer of another material on the surface of the light guide 110 .

By definition, a 'chirped' diffraction grating is a diffraction grating 130 that exhibits or has a diffraction spacing of diffractive features 132 (ie grating pitch) that varies over the range or length of the chirped diffraction grating. In some embodiments, a chirped diffraction grating may have or exhibit a chirp of diffractive feature spacing that varies linearly with distance. As such, a chirped diffraction grating is, by definition, a 'linear chirped' diffraction grating. In other embodiments, the chirped diffraction grating may exhibit a non-linear chirp of diffractive feature spacing. A variety of nonlinear chirps may be used, including, but not limited to, exponential chirps, logarithmic chirps, or other, substantially non-uniform, or chirps that vary in an arbitrary but still monotonous manner. Non-monotonic chirps such as sinusoidal chirps or triangular or sawtooth chirps may also be employed. Any combination of these types of chirps may also be employed.

6 illustrates a top view of a directional backlight 100 in an example, in accordance with an embodiment consistent with the principles described herein. In FIG. 6 , an illumination volume 134 in angular space is shown which is the distance D from the input position 116 of the light source 120 on the side 114 of the light guide 110 . It is noted that the illumination volume has a wider angular magnitude as the radial direction of propagation of the plurality of guided light beams 112 changes away from the y-axis and angles toward the x-axis. For example, illumination volume 134b is wider than illumination volume 134a as shown.

Referring back to FIG. 3B , the diffraction grating array 130 may be positioned at or adjacent to the first surface 110 ′ of the light guide 110 , which is the light beam emitting surface of the light guide 110 as shown. . For example, the diffraction grating 130 may be a transmission mode diffraction grating configured to diffractively scatter a portion of the guided light through the first surface 110 ′ as the emitted light 102 . Alternatively (not shown), the array of diffraction gratings 130 is on or at the second surface 110 ″ opposite the light beam emitting surface (ie, first surface 110 ′) of the light guide 110 . In particular, the diffraction grating 130 may be a reflective mode diffraction grating. As a reflective mode diffraction grating, the diffraction grating 130 diffracts a portion of the guided light and separates the portion of the diffracted guided light. 1 is configured to reflect toward and exit through the first surface 110' as diffractively scattered or emitted light 102. In another embodiment (not shown), the diffraction grating 130 ) may be positioned between the surface of the light guide 110 as one or both of a transmission mode diffraction grating and a reflection mode diffraction grating, for example.

In some embodiments, the diffraction grating 130 of the diffraction grating array is configured to provide unidirectional diffractive scattering with unidirectionality. The unidirectional diffractive scattering in the unidirectional direction may preferentially and in some embodiments exclusively provide the emitted light 102 from or through the first surface 110 ′ as opposed to the second surface 110 ″. In some embodiments, the diffraction grating 130 configured to provide unidirectional diffraction scattering comprises a tilted diffraction grating In other embodiments, the diffraction grating 130 configured to provide unidirectional diffraction scattering includes the diffraction grating 130 ) and a reflective material layer (not shown), the reflective material layer being an opposing diffraction grating provided with unidirectional diffraction scattering from, for example, a reflective material layer acting as a reflector or mirror. It may be located on the side of 130 .

In some embodiments, a guided light beam within the directional backlight 100, particularly when the pseudo-reflecting source causes the emission of a light beam in an unintended direction, thus resulting in an unintended image in a display employing the directional backlight 100 . To mitigate, in some instances, even substantially eliminate, various sources of these pseudo-reflexes of 112 may be provided. Examples of various potential pseudo-reflection sources include, but are not limited to, the sidewalls of light guide 110 that can create secondary reflections of guided light beam 112 . Reflections from various quasi-reflection sources within directional backlight 100 may be mitigated by any of a number of methods including, but not limited to, absorption and controlled redirection of quasi-reflections.

7A shows a top view of a directional backlight 100 including pseudo-reflection mitigation in an example, in accordance with an embodiment consistent with the principles described herein. 7B shows a top view of a directional backlight 100 including pseudo-reflection mitigation in an example, in accordance with another embodiment consistent with the principles described herein. In particular, FIGS. 7A and 7B show a directional backlight 100 including a light guide 110 , a light source 120 , and a diffraction grating array 130 . Also shown is a plurality of guided light beams 112 with at least one of the plurality of guided light beams 112 incident on the sidewalls 114a and 114b of the light guide 110 . The potential quasi-reflection of the guided light beam 112 by the sidewalls 114a, 114b is shown with dashed arrows indicating the reflected guided light beam 112'.

In FIG. 7A , the directional backlight 100 further includes an absorbing layer 119 on the sidewalls 114a , 114b of the light guide 110 . The absorbing layer 119 is configured to absorb incident light from the guided light beam 112 . The absorbing layer may comprise substantially any optical absorbing agent including, but not limited to, for example, black paint applied to the sidewalls 114a, 114b. As shown in FIG. 7A , the absorber layer 119 is applied to the sidewall 114b, while the sidewall 114a is devoid of the absorber layer 119 by way of example and not limitation. The absorbing layer 119 intercepts and absorbs the incident guided light beam 112 , effectively preventing or mitigating the creation of potential spurious reflections from the sidewall 114b. On the other hand, the guided light beam 112 incident on the sidewall 114a results in the creation of a reflected guided light beam 112', as shown by way of example and not limitation.

7B illustrates pseudo-reflection relaxation using controlled angle of reflection. In particular, the light guide 110 of the directional backlight 110 shown in FIG. 7B includes inclined sidewalls 114a and 114b. The beveled sidewalls have a beveled angle configured to preferentially direct the reflected guided lightbeam 112 ′ substantially away from the diffraction grating 130 . As such, the reflected guided light beam 112 ′ is not diffractively coupled out of the light guide 110 as an unintended beam of emitted light. The angle of inclination of the sidewalls 114a, 114b may be in the x-y plane as shown. In another example (not shown), the angle of inclination of the sidewalls 114a , 114b is xz to direct another plane, eg, the reflected guided lightbeam 112 ′, out of the upper or lower surface of the light guide 110 . may be on a flat surface. It is noted that FIG. 7B shows, by way of example and not limitation, sidewalls 114a , 114b comprising slopes along only a portion thereof.

In some embodiments, directional backlight 100 may be transparent or substantially transparent. In particular, in some embodiments, the light guide 110 and the spaced-apart diffraction grating array 130 allow light to pass through the light guide 110 in a direction orthogonal to both the first surface 110' and the second surface 110". Thus, the light guide 110 and more generally the directional backlight 100 propagate in a direction orthogonal to the general propagation direction 103 of the guided light beam 112 of the plurality of guided light beams. Transparency may also be facilitated, at least in part, by the substantially transparency of the diffraction grating 130 .

In accordance with some embodiments of the principles described herein, a backlit display is provided. The backlit display is configured to emit light provided by the backlit display. In addition, the emitted light may be modulated by a backlight display to provide or display an image. In some embodiments, the displayed image may be a multi-view image and the backlight display may be a multi-view display. In some examples, the multiview display is configured to present or 'display' a 3D image.

8 shows a block diagram of a backlit display 200 in an example, in accordance with an embodiment consistent with the principles described herein. In accordance with various embodiments, the backlit display 200 is configured to display or provide a displayed image. In particular, the emitted light 202 modulated and provided by the backlight display 200 is used to display an image. The emitted light 202 is shown as an arrow emanating from the backlit display 200 in FIG. 8 .

The backlight display 200 shown in FIG. 8 includes a light guide 210 . In some embodiments, the light guide may be substantially similar to the light guide 110 of the directional backlight 100 described above. In particular, the light guide 210 may be a plate light guide in some embodiments.

Also, as shown in FIG. 8 , the backlight display 200 includes a light source 220 positioned on the side of the light guide 210 . The light source 220 is configured to provide a plurality of guided light beams 204 having different radial directions from each other within the light guide 210 . In some embodiments, light source 220 may be substantially similar to light source 120 described above with respect to directional backlight 100 . In particular, the light source 220 may be located, for example, in the middle or near the center of the light guide side. In some embodiments, the light source 220 may be located in a cavity within the light guide 210 side. The cavity may have a shape configured to diffuse the plurality of guided light beams 204 in different radial directions. For example, the cavity may have a semicircular shape or a facet shape. As such, the cavity may be substantially similar to the cavity 122 described above.

The backlight display 200 shown in FIG. 8 further includes a diffraction grating array 230 on the surface of the light guide 210 . Individual diffraction gratings 230 of the diffraction grating array are configured to scatter light of the plurality of guided lightbeams as emitted light 202 . In some embodiments, array 230 of diffraction gratings may be substantially similar to array 130 of diffraction gratings of directional backlight 100 described above. In particular, the grating characteristics of the individual diffraction gratings 230 of the diffraction grating array are configured to determine the intensity and angular spread of the emitted light 202 . Further, the grating characteristics are a function of both the position of the individual diffraction grating 230 on the light guide surface and the position of the light source on the side of the light guide 210 , according to various embodiments. In some embodiments, the grating characteristics may also determine the principal angular direction of the emitted light 202 . According to various embodiments, the emitted light 202 collectively scattered by the individual diffraction gratings 230 is configured to have a uniform intensity and angular spread across the light valve array.

In some embodiments, grating features include one or both of a curvature and grating chirp of an individual diffraction grating 230 . A grating feature, which is one or both of curvature and grating chirp, for example, may be configured to determine the angular spread of emitted light 202 scattered by individual diffraction grating 230 . Further, in some embodiments, the diffraction grating array 230 may be configured to provide unidirectional diffractive scattering having a unidirectional direction. In these embodiments, individual diffraction gratings 230 of the diffraction grating array may include one or both of a reflective mode diffraction grating (eg, with a layer of reflective material) and a tilted diffraction grating.

According to various embodiments, the backlight display 200 further includes a light valve array 240 . The light valve array 240 is configured to modulate the emitted light 202 to provide a displayed image. A dashed line is used in FIG. 8 to highlight the modulation of the emitted light 202 after passing through the light valve array 240 . In various embodiments, different types of light valves are employed as light valves 240 of a light valve array including, but not limited to, one or more of liquid crystal light valves, electrophoretic light valves, and electrowetting based light valves. can be

In accordance with some embodiments, individual diffraction gratings 230 of the diffraction grating array are each configured to scatter the light of the plurality of guided lightbeams as emitted light 202 comprising a plurality of directional lightbeams having different principal angular directions. do. In some of these embodiments, different principal angular directions may correspond to respective different viewing directions of the multiview image. As such, the backlight display is a multi-view display and the displayed image is a multi-view image. Further, individual diffraction gratings 230 may be multi-beam elements, and light valve sets 240 may correspond to multi-view pixels of a multi-view display. As a multi-beam element, the individual diffraction gratings 230 may be sized about half to twice the size of the light valves 240 or equivalent to the center-to-center spacing between the light valves 240 . Also, in some embodiments, individual diffraction gratings 230 may have a shape similar to that of a multi-view pixel.

According to another embodiment of the principles described herein, a method of operating a directional backlight is provided. 9 shows a flow diagram of a method 300 of directional backlight operation in an example, in accordance with embodiments consistent with the principles described herein. According to various embodiments, the method 300 of directional backlight operation may be used to provide light to illuminate a backlight display and thus display an image.

As shown in FIG. 9 , a method 300 of directional backlight operation includes guiding light 310 along a light guide as a plurality of guided lightbeams having a common origin and different radial directions. In particular, a guided lightbeam of the plurality of guided lightbeams by definition has a different radial propagation direction than another guided lightbeam of the plurality of guided lightbeams. Further, each guided lightbeam of the plurality of guided lightbeams has a common origin by definition. In some embodiments, the origin may be a virtual origin (eg, a point beyond the real origin of the guided light beam). For example, the origin may be outside of the light guide and thus may be a virtual origin. According to some embodiments, as described above with reference to directional backlight 100 , light guide 310 for guiding light and a guided light beam guided therein are light guide 110 and guided light beam 112 , respectively. ) may be substantially similar to

The method 300 of directional backlight operation shown in FIG. 9 further includes scattering ( 320 ) the light of the plurality of guided light beams 320 as emitted light using a diffraction grating of the diffraction grating array. Light emitted from the diffraction grating has an intensity and angular spread that is a function of the position of the diffraction grating with respect to a common origin of the plurality of guided light beams, according to various embodiments. Further, in accordance with various embodiments, the emitted light collectively scattered by the diffraction grating array has a uniform intensity and angular spread across the surface of the light guide. In some embodiments, the diffraction grating array used to scatter light 320 may be substantially similar to the diffraction grating array 130 of the directional backlight 100 described above. Also, the emitted light produced by the scattering 320 may be substantially similar to the emitted light 102 as described above.

In particular, the emitted light scattered 320 by the diffraction grating array has an intensity, a principal angular direction, and an angular spread, in accordance with various embodiments. Each of the intensity, principal angular direction, and angular spread is controlled or determined by grating characteristics of the diffraction grating of the diffraction grating array. In addition, the grating feature is determined by the location of the diffraction grating on the surface of the light guide and

It is a function of both the common origin of the light beam (eg, the position of the light source on the side of the light guide). In particular, the grating characteristics of the diffraction grating array may vary based on the radial direction of the guided light beam incident on the diffraction grating, the distance from the diffraction grating to the light source providing the guided light beam, or both, or equivalently their It can be a function.

In some embodiments, scattering light 320 includes unidirectional diffractive scattering in a unidirectional direction. In particular, the diffraction grating of the diffraction grating array may comprise one or both of a tilted grating and a diffraction grating and a reflective mode diffraction grating comprising a layer of reflective material.

As shown, the method 300 of directional backlight operation further includes providing 330 light to be guided as a plurality of guided light beams using a light source. In particular, light is provided to the light guide as a guided light beam having a plurality of different radial propagation directions using a light source. According to various embodiments, the light source used to provide 330 light is located on the side of the light guide, the light source location being a common origin of the plurality of guided light beams. In some embodiments, the light source may be substantially similar to the light source(s) 120 of the directional backlight 100 described above. For example, the light source may be butt-coupled to or to the edge of the light guide. In another example, the light source may approximate a point circle representing a common origin. In another example, the light source may be positioned within a cavity on the side of the light guide, the cavity having a shape configured to diffuse a plurality of guided light beams in different radial directions.

In some embodiments, provided 330 light is substantially uncollimated. In another embodiment, provided 330 light may be collimated (eg, the light source may comprise a collimator). In various embodiments, provided 330 light may be guided with different radial directions at a non-zero propagation angle within the light guide between the surfaces of the light guide. When collimated within the light guide, provided 330 light may be collimated according to a collimation factor to establish a desired angular spread of guided light within the light guide. In particular, the desired angular spread provided by the collimate and thus the collimate factor may be in the vertical direction.

In some embodiments (not shown), the method 300 of directional backlight operation further comprises modulating the emitted light collectively scattered 320 by the diffraction grating array. Modulation may be provided by or using a light valve array to provide a displayed image. In some embodiments, the light valve array may be substantially similar to the light valve array 240 of the backlight display 200 described above. Also, in some embodiments, the displayed image may be a multi-view image.

Accordingly, examples and embodiments of directional backlights, backlight displays, and methods of operating a directional backlight having a diffraction grating configured to provide emitted light with uniform intensity and angular spread have been described. It is to be understood that the examples described above are illustrative of some of the many specific examples that are representative of the principles described herein. Obviously, those skilled in the art can readily devise numerous other arrangements without departing from the scope defined by the following claims.

Claims (21)

A directional backlight comprising:
a light guide configured to guide the light beams;
a light source configured to provide a plurality of guided light beams having different radial directions within the light guide; and
an array of diffraction gratings spaced apart from each other on a surface of the light guide, the diffraction gratings of the grating array scattering a portion of the guided lightbeam of the plurality of guided lightbeams as emitted light having an intensity, a principal angular direction, and an angular spread comprising the diffraction grating array configured to
the emitted light collectively scattered by the diffraction gratings of the diffraction grating array is configured to have a uniform intensity and angular spread across the surface of the light guide;
one or both of a grating pitch and a grating orientation of the diffraction grating of the diffraction grating array are configured to determine the principal angular direction of a directional lightbeam of the emitted light scattered by the diffraction grating;
wherein the grating pitch and the grating orientation are a function of the position of the diffraction grating along the radial direction of the guided light beam corresponding to the diffraction grating;
directional backlight. The directional backlight of claim 1 , wherein the light source is located on the side of the light guide at a midpoint on the side. The directional backlight of claim 1 , wherein the light source is positioned within a cavity within a side of the light guide, the cavity having a shape configured to diffuse the plurality of guided light beams in the different radial directions. 2. The grating feature of claim 1, wherein a grating feature of the diffraction grating is configured to determine the intensity and the angular spread of the emitted light scattered by the diffraction grating, the grating feature of the diffraction grating on the surface of the light guide. a function of both the position of the diffraction grating and the position of the light source on the side of the light guide. 5. The directional backlight of claim 4, wherein the grating feature comprises a grating depth configured to determine the intensity of the emitted light scattered by the diffraction grating. delete 5. The directivity of claim 4, wherein the grating feature comprises one or both of a curvature and a grating chirp of the diffraction grating, the grating feature configured to determine the angular spread of the emitted light scattered by the diffraction grating. backlight. The directional backlight of claim 1 , wherein the diffraction grating is configured to provide unidirectional diffractive scattering having a unidirectional direction. The directional backlight of claim 8 , wherein the diffraction grating configured to provide unidirectional diffraction scattering comprises a tilted diffraction grating. 9. The directional backlight of claim 8, wherein the diffraction grating configured to provide unidirectional diffractive scattering is a reflective mode diffraction grating comprising a diffraction grating and a layer of reflective material. A backlight display comprising the directional backlight of claim 1 , wherein the backlight display further comprises an array of light valves configured to modulate the emitted light to provide a displayed image. In a backlight display,
light guide;
a light source positioned on a side of the light guide and configured to provide a plurality of guided light beams having different radial directions from each other within the light guide;
a diffraction grating array on a surface of the light guide, wherein individual diffraction gratings of the diffraction grating array are configured to scatter light of the plurality of guided light beams as emitted light; and
a light valve array configured to modulate the emitted light to provide a displayed image;
the emitted light collectively scattered by the individual diffraction gratings is configured to have a uniform intensity and angular spread across the light valve array;
one or both of the grating pitch and grating orientation of the individual diffraction gratings of the diffraction grating array are configured to determine a principal angular direction of directional light beams of the emitted light scattered by the individual diffraction gratings;
wherein the grating pitch and the grating orientation are a function of the position of the individual diffraction gratings along the radial direction of the guided light beams corresponding to the individual diffraction gratings;
backlit display. The backlight display of claim 12 , wherein the light source is located within a cavity within the side of the light guide, the cavity having a shape configured to diffuse the plurality of guided light beams in the different radial directions. 13. The method of claim 12, wherein a grating characteristic of an individual diffraction grating of the diffraction grating array is configured to determine an intensity and an angular spread of the emitted light, the grating characteristic comprising: a position of the individual diffraction grating on a surface of the light guide; a function of both the position of the light source on the side of the light guide. 15. The method of claim 14, wherein the grating feature comprises one or both of a curvature and a grating chirp of the respective diffraction grating, the grating feature determining the angular spread of the emitted light scattered by the respective diffraction grating. A backlit display configured to: 13. The diffraction grating of claim 12, wherein the array of diffraction gratings is configured to provide unidirectional diffraction scattering having a unidirectional direction, and wherein the individual diffraction gratings of the diffraction grating array are one of a reflective mode diffraction grating and a tilted diffraction grating; A backlit display, including both. 13. The plurality of guides as recited in claim 12, wherein said individual diffraction gratings of said diffraction grating array comprise a plurality of directional light beams having different principal angular directions corresponding to respective different viewing directions of a multi-view image. a backlight display, each configured to scatter light of the illuminated light beams, wherein the backlight display is a multi-view display and the displayed image is the multi-view image. A method for operating a directional backlight comprising:
guiding in a light guide a plurality of guided lightbeams having a common origin and different radial directions; and
scattering the light of the plurality of guided light beams as emission light using a diffraction grating of a diffraction grating array, wherein the emission light from the diffraction grating is directed to the diffraction grating relative to the common origin of the plurality of guided light beams. having an intensity and an angular spread that is a function of the position of
the emitted light collectively scattered by the diffraction grating array has a uniform intensity and angular spread across the surface of the light guide;
one or both of a grating pitch and a grating orientation of the diffraction grating of the diffraction grating array are configured to determine a principal angular direction of a directional light beam of the emitted light scattered by the diffraction grating;
wherein the grating pitch and the grating orientation are a function of the position of the diffraction grating along the radial direction of the guided light beam corresponding to the diffraction grating;
Way. 19. The method of claim 18, further comprising providing the plurality of guided light beams within the light guide using a light source positioned within a cavity on a side of the light guide, wherein the cavity directs the plurality of guided light beams. having a shape configured to diffuse in the different radial directions. 19. The method of claim 18, wherein scattering light comprises unidirectional diffraction scattering in a unidirectional direction, wherein the diffraction grating comprises one or both of a tilted diffraction grating and a reflective mode diffraction grating, the reflective mode wherein the diffraction grating comprises a diffraction grating and a layer of reflective material. 19. The method of claim 18, further comprising modulating the emitted light collectively scattered by the diffraction grating array using a light valve array to provide a displayed image.

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